Car is slightly jolting/stuttering
Discussion
So for the past week I've noticed a slight un-smoothness to the performance of my car. When I'm cruising and holding a speed, irrespective of what speed I'm doing or gear I'm in I've occassionally noticed a bit of jolting. That is to say, every now and then the car feels like it accelerates/decelerates ever so slightly and for a matter of milliseconds. This is all whilst maintaining a constant pressure on the accelerator pedal. At first I wondered if it was my mind playing tricks on me, it's that small an effect.
Over the course of the week I've become certain that something isn't quite right as I continue to notice it. The car seems to be running ok but for this small niggle, although I can't help but feel it doesn't have it's full complement of power - again, could be my mind playing tricks.
Has anyone else experienced something similar and if so, did you find out what the cause was? I'd like to try and rectify this myself if anyone has suggestions otherwise I might have to take another trip to Racing Green! Having done 2000 miles in 3 weeks since getting her back (how is it my TVR is proving more reliable than my Saab?!) but not having had any review done around the engine's health whilst she was in the shop for boywork, I might be well advised to have the engine given a general health check anyway, any thoughts on this e.g. cost, tests they can do on health/performance etc? I'd just love to be able to drive her without any niggling thoughts in the back of my mind that something might be wrong!
Over the course of the week I've become certain that something isn't quite right as I continue to notice it. The car seems to be running ok but for this small niggle, although I can't help but feel it doesn't have it's full complement of power - again, could be my mind playing tricks.
Has anyone else experienced something similar and if so, did you find out what the cause was? I'd like to try and rectify this myself if anyone has suggestions otherwise I might have to take another trip to Racing Green! Having done 2000 miles in 3 weeks since getting her back (how is it my TVR is proving more reliable than my Saab?!) but not having had any review done around the engine's health whilst she was in the shop for boywork, I might be well advised to have the engine given a general health check anyway, any thoughts on this e.g. cost, tests they can do on health/performance etc? I'd just love to be able to drive her without any niggling thoughts in the back of my mind that something might be wrong!
I've just found the following thread referring to overfilling the oil:
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
I put a bit too much oil in the car recently due to not being able to get an accurate reading of the oil level. I'm not suffering any of the major symptoms that Funky Jo mentions but I am a little worried that the overfill might be what's causing my issues, the symptoms I'm experiencing certainly seemed to coincide with me adding oil when I wasn't sure of the level. Thoughts?
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
I put a bit too much oil in the car recently due to not being able to get an accurate reading of the oil level. I'm not suffering any of the major symptoms that Funky Jo mentions but I am a little worried that the overfill might be what's causing my issues, the symptoms I'm experiencing certainly seemed to coincide with me adding oil when I wasn't sure of the level. Thoughts?
Assuming the car is well serviced and was fairly recently... Check both exhaust can outlets.... is one or both sooty black - if so check the lambda's, check the throttle pots an check the throttle butterflies. If you know what you are doing then it might be worth obtaining a lead and the ECU software so you can see what is happening. I no longer have the MBE ECU in my car but I am pretty sure with the MBE you can map the sensors on a laptop whilst running the car. You should be able to see if the lambda's and or the throttle pots are playing up. You can also reset the adaptive maps (derived from the lambda readings). Worth checking the routing of the ignition leads if they are too close to the crank sensor pick up lead (despite it being shielded and earthed) you can get induced pick up on the trigger signal. If the throttle butterflies are fluctuating (worn bushes or throttle bodies - depends on year/mileage of your car) this will create havoc for the throttle pots, this should show up if you map the TP signals (there's 2, one each end of the throttle rail). It could also be plugs, plug leads, coil pack etc.... etc... I am pretty sure some of the other guys will pop along with more idea's
Good luck - failing that take it to a reputable TVR garage.
.... Just had another thought....the airbox is not a well made item and have been known to break up where they mate with the throttle bodies and leak air, weakening the mixture. Check your plugs are all roughly the same colour,
Good luck - failing that take it to a reputable TVR garage.
.... Just had another thought....the airbox is not a well made item and have been known to break up where they mate with the throttle bodies and leak air, weakening the mixture. Check your plugs are all roughly the same colour,
Edited by yzf1070 on Wednesday 24th March 13:12
yzf1070 said:
Assuming the car is well serviced and was fairly recently... Check both exhaust can outlets.... is one or both sooty black - if so check the lambda's, check the throttle pots an check the throttle butterflies. If you know what you are doing then it might be worth obtaining a lead and the ECU software so you can see what is happening. I no longer have the MBE ECU in my car but I am pretty sure with the MBE you can map the sensors on a laptop whilst running the car. You should be able to see if the lambda's and or the throttle pots are playing up. You can also reset the adaptive maps (derived from the lambda readings). Worth checking the routing of the ignition leads if they are too close to the crank sensor pick up lead (despite it being shielded and earthed) you can get induced pick up on the trigger signal. If the throttle butterflies are fluctuating (worn bushes or throttle bodies - depends on year/mileage of your car) this will create havoc for the throttle pots, this should show up if you map the TP signals (there's 2, one each end of the throttle rail). It could also be plugs, plug leads, coil pack etc.... etc... I am pretty sure some of the other guys will pop along with more idea's
Good luck - failing that take it to a reputable TVR garage.
.... Just had another thought....the airbox is not a well made item and have been known to break up where they mate with the throttle bodies and leak air, weakening the mixture. Check your plugs are all roughly the same colour,
what he said Good luck - failing that take it to a reputable TVR garage.
.... Just had another thought....the airbox is not a well made item and have been known to break up where they mate with the throttle bodies and leak air, weakening the mixture. Check your plugs are all roughly the same colour,
Edited by yzf1070 on Wednesday 24th March 13:12
Could be any number of things, i would start with ignition then start looking at things linke lambdas, throttle pots, throttle bodies etc...get the laptop plugged in may give you a clue where to start...
I suffered this but i describe it as mild shunting trying to keep a steady motorway speed i find it annoying and this was bringing it back home after a service!.
To be fair the car was new to me so would of been there before the service i weas told more than likely throttle pots £75 for the pair.
I fitted them and it's been fine since rear one is tricky to fit
To be fair the car was new to me so would of been there before the service i weas told more than likely throttle pots £75 for the pair.
I fitted them and it's been fine since rear one is tricky to fit
Fully appreciate all the advice. I'll get the cable next week and may come back to ask for some help with analysis of the data, hopefully that will shed some light.
Out of interest, do the symptoms I'm mentioning and the various possible solutions correlate with the fact that the car feels a bit down on power?
Out of interest, do the symptoms I'm mentioning and the various possible solutions correlate with the fact that the car feels a bit down on power?
They are classic worn throttle pot / body symptoms, but need to check the obvious first as they are a relatively expensive fix! The cheapest is Racing greens reconditioned set @ £330, but they are a fit yourself job - you need to be confident you can do it and then set the engine up.
Do you have a misfire at high revs - circa 5 / 5.5k rpm? another classic sign.
Be aware that throttle pots have their own spring return internals that may help with staying in tune if you fit brand new ones, but if the throttle bodies are worn you will in turn wear the throttle pots out a damn site quicker.
All i am saying is if the throttle bodies are worn replacing the throttle pots is a sticking plaster fix and not the route casue of your issues, it will come back.
oh and edited to say, if its gone out of tune, due to worn throttle pots / air leaks etc i.e incorrect AFR then yes it will feel 'dull' compared to a properly tuned engine (mine did), but the difference in reality isnt huge.
Do you have a misfire at high revs - circa 5 / 5.5k rpm? another classic sign.
Be aware that throttle pots have their own spring return internals that may help with staying in tune if you fit brand new ones, but if the throttle bodies are worn you will in turn wear the throttle pots out a damn site quicker.
All i am saying is if the throttle bodies are worn replacing the throttle pots is a sticking plaster fix and not the route casue of your issues, it will come back.
oh and edited to say, if its gone out of tune, due to worn throttle pots / air leaks etc i.e incorrect AFR then yes it will feel 'dull' compared to a properly tuned engine (mine did), but the difference in reality isnt huge.
Edited by Robertjp on Friday 26th March 09:22
kronik said:
Hi Robert, gave the car a blip up to 6k revs a few times yesterday, no misfire at all....
Good sign i guess!I would say fully check the ignition system (easily checked if you work round each component part, disconnecting / swapping HT leads, plugs etc)
A laptop also needed to check its nothing obvious like a lambda or throttle pot gone?
If no luck, get it down to a specialist?
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